Foodborne pathogens isolated from foods of animal origin, investigation of the antibiotic desistance and assessment of public health riks

The overuse of antibiotics in human and veterinary medicine has been blamed for the development of resistant bacterial strains that can be spread through the food chain to the community. The objectives of the present thesis include: a) the isolation of food-borne pathogens from foods of animal origin, b) the susceptibility testing of the isolates in order to determine the prevalence of the antibiotic resistant food-pathogens and c) the assessment of the possible risk to Public Health. A total number of 870 food samples collected during a three year period (from July 2004 to August 2007) were examined. The antibiotic resistance of the isolates was determined using the Kirby-Bauer disk diffusion assay. The bacteria isolated were 252 strains of Escherichia coli, 27 strains of Yersinia enterocolitica, 4 strains of Salmonella spp., 383 strains of other Enterobacteriaceae, 95 strains of Staphylococcus aureus, 57 strains of Enterococcus spp., 6 strains of Listeria spp. and 3 strains of Campylobacter jejuni. No bacteria were isolated from thermally processed food samples. In the present study the prevalence of E.coli was 29%, of S.aureus 10.9%, of Yersinia enterocolitica 3.1%, of Salmonella spp. 0.5%, of Listeria spp. 0.7% and of Campylobacter spp. 0.3%. The prevalence of other Enterobacteriaceae was 44% and included strains of Klebsiella spp., Enterobacter spp., Citrobacter spp., Pantoea spp, Hafnia alvei, Kluyvera spp and Serratia spp. Escherichia coli strains were resistant to amikacin (31.3%), amoxycillin/clavulanic acid (31%), ampicillin (57.5%), ampicillin/sulbactam (25.4%), carbenicillin (51.2%), ceftriaxone(10.7%), cefuroxime (43.3%), ciprofloxacin (17.1%), gentamicin (29.4%), imipenem (9.9%), tetracycline (41.7%), ticarcillin (36.1%), ticarcillin/clavulanic (23.8%). Fifty four percent of the isolates showed resistance at least to three antibiotics. Staphylococcus aureus isolates showed resistance to penicillin-G (83.2%), ampicillin (65.3%), tetracycline (22.1%), amoxycillin/clavulanic acid (13.7%), to clindamycin (31.6%), ciprofloxacin (15.8%). 37.9% of S.aureus strains were resistant at least to 3 antibiotics. No methicilline or vancomycin resistant S.aureus was isolated. Yersinia enterocolitica was found resistant to ampicillin (96.3%), while 25.9% of the strains showed resistance at least to three antibiotics. Salmonella spp. strains were resistant to ampicillin (75%), amoxicillin/clavulanic acid (75%), ciprofloxacin (50%), ticarcillin/clavulanic acid (50%), ampicillin/sulbactam (25%), tetracycline (25%) and amikacin (25%). .......Η ευρεία χρήση των αντιμικροβιακών ουσιών στην ιατρική, την κτηνιατρική και τη γεωργία έχει οδηγήσει σε ανησυχητική αύξηση των ανθεκτικών στα αντιβιοτικά στελεχών βακτηρίων. Σκοπός της παρούσας διατριβής ήταν η απομόνωση και η μελέτη της ευαισθησίας στα αντιβιοτικά παθογόνων μικροοργανισμών από δείγματα τροφίμων ζωικής προέλευσης καθώς και η αξιολόγηση του κινδύνου για τη Δημόσια Υγεία. Στη διάρκεια της παρούσας 3ετούς μελέτης (Ιούλιος 2004 - Αύγουστος 2007) συλλέχθηκαν 870 δείγματα τροφίμων, τα οποία εξετάστηκαν μικροβιολογικά χρησιμοποιώντας τις αποδεκτές για τον έλεγχο των τροφίμων μεθόδους (ΙSO methods). Για τον έλεγχο της ευαισθησίας στα αντιβιοτικά των στελεχών που απομονώθηκαν χρησιμοποιήθηκε η μέθοδος της διάχυσης σε άγαρ Bauer-Kirby. Απομονώθηκαν 252 στελέχη E.coli, 27 στελέχη Y. enterocolitica, 4 στελέχη σαλμονελλών, 383 στελέχη άλλων εντεροβακτηριοειδών, 6 στελέχη Listeria spp., 3 στελέχη C.jejuni,, 57 στελέχη εντερόκοκκων και 95 στελέχη Staphylococcus aureus, τα οποία εξετάστηκαν ως προς την αντοχή τους σε διάφορα αντιβιοτικά που χρησιμοποιούνται στην ιατρική πράξη. Δεν απομονώθηκαν παθογόνα βακτήρια από τρόφιμα που είχαν υποστεί θερμική επεξεργασία. Τα βακτήρια που απομονώθηκαν από το σύνολο των δειγμάτων με τη μεγαλύτερη συχνότητα ήταν τα στελέχη E.coli (29%), S. aureus (10,9%), Y.enterocolitica (3,1%), Listeria spp. (0,7%), Salmonella spp. (0,5%) και Campylobacter spp. (0,3%). Όσο αφορά τα άλλα εντεροβακτηριοειδή, το ποσοστό απομόνωσης ήταν 44%, και περιελάμβαναν 40 στελέχη Klebsiella spp. (4,6%), 138 στελέχη Enterobacter spp. (15,9%), 187 στελέχη Citrobacter spp (21,5%), 5 στελέχη Pantoea spp (0,6%), 10 στελέχη Hafnia alvei (1,1%), ένα στέλεχος Kluyvera spp (0,1%) και δύο στελέχη Serratia spp. (0,2%). Τα στελέχη E.coli εμφάνισαν αντοχή στην αμικασίνη (31,3%), το συνδυασμό αμοξυκιλλίνη/κλαβουλανικό οξύ (31%), την αμπικιλλίνη (57,5%), το συνδυασμό αμπικιλλίνη/σουλβακτάμη (25,4%), την καρμπενικιλλίνη (51,2%), την κεφτριαξόνη (10,7%), την κεφουροξίμη (43,3%), τη σιπροφλοξασίνη (17,1%), τη γενταμικίνη (29,4%), την ιμιπενέμη (9,9%), την τετρακυκλίνη (41,7%), την τικαρσιλλίνη (36,1%), το συνδυασμό τικαρσιλλίνη/κλαβουλανικό οξύ (23,8%). Το 54% των στελεχών που απομονωθήκαν έδειξαν αντοχή σε τρία τουλάχιστον αντιβιοτικά. ...............

Detection ofCryptosporidiumandGiardiain foods of plant origin in North-Western Greece

GiardiaandCryptosporidiumare recognized as leading causes of waterborne and foodborne diarrhoeal disease with worldwide distribution. The study aimed to determine the protozoan contamination of various foods of plant origin. A total of 72 samples from 27 different varieties of fresh vegetables and fruits were collected from supermarkets and open markets in North-Western Greece and were examined using conventional diagnostic methods. Two out of 72 (2.8%) samples were found positive forCryptosporidiumoocysts, while no sample was found to be positive forGiardiacysts. The results show the presence of protozoan contamination in foods of plant origin, which may constitute a potential health hazard

Characterization of Extended Spectrum Cephalosporin-Resistant <i>Escherichia coli</i> Strains Isolated from Raw Poultry Carcasses in Catering Services in Northern Greece

Antimicrobial resistance is considered a topic of utmost interest under the concept of “One Health”, having severe implications in both human and veterinary medicine. Among the antibiotic-resistant bacteria, gram-negative bacteria, especially those belonging to the order of Enterobacterales (such as Escherichia coli), hold a prominent position in terms of both virulence and possessing/disseminating antimicrobial resistance (AMR) traits. The aim of this study was to examine the presence of extended-spectrum β-lactamase producing E. coli isolates in raw poultry carcasses collected from a university club. Five hundred raw poultry skin samples were collected from the Aristotle University of Thessaloniki (AUTh) club in Thessaloniki, Greece. A total of 64% of the samples were positive for the presence of extended-spectrum β-lactamase (ESBL)-producing E. coli. The isolates were further examined for their susceptibility to selected antibiotics by the disc diffusion method and were characterized as true ESBL, as producing class C cephalosporinases (AmpC) or “of unknown etiology” by the combination disc test. The 86 of the 120 isolates (71.67%) were classified as true ESBL, 24 (20.00%) as AmpC, and 10 (8.33%) as “of unknown etiology”. The isolates were screened for the occurrence of β-lactamase genes (blaTEM, blaCTX-M, blaSHV, and blaOXA). Thirty-six isolates (32 ESBL- and 4 AmpC-phenotype) harbored both blaTEM and blaCTX-M genes, twenty-two isolates (among which 19 ESBL-phenotype and 2 AmpC-phenotype) harbored blaCTX-M only, whereas twenty-six (14 ESBL- and 12 AmpC-phenotype) isolates harbored blaTEM alone. No isolate harboring blaSHV or blaOXA was detected. The results demonstrate the existence of E. coli isolates producing extended-spectrum β-lactamases in poultry carcasses from Greece, pausing a risk for antibiotic resistance transfer to humans

Antibacterial Efficacy of Commercially Available Essential Oils Tested Against Drug-Resistant Gram-Positive Pathogens

The potential antibacterial activity of basil (Ocimum basilicum), chamomile (Matricaria chamomilla), origanum (Thymus capitatus), tea tree (Melaleuca alternifolia) and thyme (Thymus vulgaris) essential oils, was investigated against 29 Gram-positive bacterial strains isolated from wastewater treatment plants, clinical samples (n = 25) and American Type Culture Collection (ATCC) reference strains (n = 4). Wild bacterial strains included methicillin-resistant Staphylococcus aureus (n = 16) and vancomycin-resistant Enterococcus spp. (n = 9). The antimicrobial activity of the selected oils was studied using the broth macrodilution method. The Minimal Inhibitory Concentration (MIC) values for S. aureus ranged from 0.06 to 0.5% (v/v) for origanum oil, 0.06 to 1% (v/v) for thyme oil, 0.12 to 1% (v/v) for tea tree oil, 0.25 to 4% (v/v) for basil oil and 2 to &gt;4% (v/v) for chamomile oil. For enterococci the MIC values were significantly higher ranging from 0.25 to 1% (v/v), 0.5 to 2% (v/v), 1 to 4% (v/v), 4 to &gt;4% (v/v) and &gt;4% (v/v) for the above-mentioned oils, respectively. The main compounds of the tested essential oils were: estragole (Ocimum basilicum), bisabolol and trans-b-farnesene (Matricaria chamomilla), carvacrol and thymol (Thymus capitatus), terpinen-4-ol and p-cymene (Melaleuca alternifolia), thymol, linalool, and p-cymene (Thymus vulgaris). Origanum essential oil yielded the best antimicrobial results followed by thyme, tea tree, and basil oil, while chamomile oil exhibited weak antibacterial properties